This invention relates to a particularly advantageous process for the liquid phase N-alkylation of an aromatic amine by reacting the amine with an alcohol in the presence of phosphoric acid.
It is known that aniline can be alkylated by passing a mixture of methanol and aniline through hot concentrated phosphoric acid (DT-PS No. 1,031,796). One disadvantage of this process is that N,N-dialkyl compounds, especially those with alkyl radicals other than the methylradical, are difficult to obtain on a commercial scale in this way. Other disadvantages are that the product always contain a considerable quantity of N-monoalkyl compound as a secondary product in addition to the N,N dialkyl compounds, and that the catalyst used loses activity after prolonged use.